Culture on My Mind
Speed of Light
May 2, 2022
This week, I have physics on my mind, courtesy of a meme.
The meme presents some interesting concepts that can be confusing to think about. They also require a few assumptions, as science usually does.
The speed of light in a vacuum is an important physical constant in physics. The value is commonly denoted as c and is exactly defined as 299,792,458 meters/second (though easy figures for simplicity are 300,000 km/second and 186000 miles/second). Basically, light can circle our planet about 7.5 times in one second.
In terms of the special theory of relativity, this physical constant is the upper limit for the speed at which conventional matter, energy, or any signal carrying information can travel through space. It also defines the relationship between energy and mass – E=mc2 – which suggests that a tremendous amount of energy is needed to accelerate any mass to that speed.
All forms of electromagnetic radiation – light, radio, etc – travel at the speed of light and we can measure the distance that they travel through space. We put a lot of signals out into space from our planet, and the distance those signals travel through a vacuum in one year is defined as a light-year.
That brings us back to the meme.
If a ship was parked one light-year away from the planet, the light and signals that reached them would be from one year in our past. We would be living in 2022, but they’d be seeing information from 2021 since that was when those signals were broadcast.
If that ship was parked 53 light-years away, they would be able to watch humans land on the Moon for the first time. Those television signals were generated in 1969.
Since light is an electromagnetic signal, we can use telescopes like Hubble or James Webb to capture that light and study the past. The light coming from a star one million light-years away shows us what was happening there one million years ago. If there was a habitable planet around that star and we had a sufficiently powerful telescope, we could theoretically see what life was like on that planet one million years ago.
It’s a difficult concept for some people to understand, but it’s exactly why we send telescopes like Hubble and James Webb up there. By studying the light from stars so far away, we can begin to understand the formation of the universe. We could even look back to its very beginnings.
The meme is simple, but the science is awesome.
What I have here is very bare bones, but the science from Ole Rømer to James Clerk Maxwell and Albert Einstein is easy to read about. It’s fascinating stuff.
If you want more science stuff from this site, check out my feature STEAM Saturday, in which I gather some interesting stuff from science, technology, engineering, art, and mathematics to share with you. I publish that (roughly) every two weeks.
Culture on My Mind is inspired by the weekly Can’t Let It Go segment on the NPR Politics Podcast where each host brings one thing to the table that they just can’t stop thinking about.
For more creativity with a critical eye, visit Creative Criticality.